NSC is WSC+starch. Sometimes you'll see sugar and starch on a feed label. I believe if you add up the two they add up to NSC. WSC is ESC+ fructans. The group recommends looking at ESC+starch, though some horses really need to account for fructans. For these, its WSC+starch (aka sugar+starch or NSC) to look at. Mine are hypersensitive, so I personally always look at NSC. If you have a less sensitive horse, ESC+starch should be fine.
I have a couple ideas to share with you. The first is turmeric. My horses go crazy for the stuff, to the point where I have to lock my minis away when I syringe feed supplements to my metabolic pony. They absolutely love the stuff.
I've heard good things about fenugreek seed too. Haven't tried it yet, but I should get my first batch soon.
Another idea would be to look at the picky eater file and go through that, to make sure there's nothing else going on.
Hope this helps.